1. Field of the Invention
The present invention relates to an apparatus for measuring alternating current (AC) loss of a superconductor.
2. Description of the Related Art
Methods for measuring AC loss of superconductors include a temperature measurement method in which a temperature rise in a superconductor upon application of an AC magnetic field is measured, and an evaporation method in which the quantity of evaporation of a refrigerant upon application of an AC magnetic field is measured. The temperature measurement method has an advantage over the evaporation method in that measurement accuracy is higher and the time constant of temperature variation at the time when a heating output is applied or cut off is shorter (see, for example, JP-7-27725-A). In the example described in the patent document, the specimen is surrounded by a medium, having low thermal conductivity, which serves as a thermal resistance with respect to the surrounding liquid helium bath.